Paul Cleary | CSIRO - Academia.edu (original) (raw)
Papers by Paul Cleary
Surface and Coatings Technology, 2014
ABSTRACT Cold spray is a manufacturing process that has proved to be a valuable technique for pro... more ABSTRACT Cold spray is a manufacturing process that has proved to be a valuable technique for producing high strength metallic coatings. It has been extensively studied in recent years, both experimentally and computationally. Among the various modelling investigations in the literature, a large number have considered the problem of a single particle impacting a substrate by means of a continuum technique, most commonly the finite element method. These models that have been used previously are generally based on two inadequate assumptions, namely 1) both particle and substrate are assumed to initially be at room temperature, and 2) the experimentally observed increase in strain rate sensitivity of the flow stress at high strain rates is ignored. To investigate the combined effect of temperature and strain rates, a three-dimensional model of a single particle impact with a metallic substrate has been developed using Smoothed Particle Hydrodynamics. This meshless method is ideally suited to the simulation of Cold Spray as very large material deformations can be readily accommodated, whereas this is often a significant difficulty in mesh based techniques. A Cu-on-Cu impact was considered and quantitative comparisons with experimental cross sections were conducted. It was found that predictions within 5% of the experimental data could be achieved only when both the softening effect due to the initial thermal field and the hardening effect due to the very high strain rates were included in the model. In contrast ignoring these effects led to results that had as much as 50% variation compared to experiments. The model described in this paper is a robust tool that will enable quantitative predictions of cold spray impacts and help further optimize the process.
Publication details, including instructions for authors and subscription information: To cite thi... more Publication details, including instructions for authors and subscription information: To cite this Article Owen, P. J., Cleary, P. W. and Mériaux, C.'Quasi-static fall of planar granular columns: comparison of 2D and 3D discrete element modelling with laboratory experiments', Geomechanics and Geoengineering, 4: 1, 55 — 77 We investigate the fall of planar granular columns in a quasi-static regime using a combination of laboratory experiments and simulations using the discrete element method (DEM). Columns made of alternately coloured sand layers are initially laid out in a box and then released when a retaining wall is set in slow motion with constant speed. The flow of the sand involves failure of the granular material along multiple slip planes at different stages of the deformation, leading to complex flow patterns. DEM simulations, in 2D and 3D, are able to qualitatively and quantitatively reproduce a range of essential elements of this flow, with particle shape being an important contributor to the mobilisation of specific slip planes. We also examine the sensitivity of the DEM predictions to changes in the operating, material and simulation parameters. We find that DEM predictions are invariant to changes of moving wall speed, spring stiffness, particle-particle friction and particle-wall friction. Conversely, they are quite sensitive to the shape of the particles. In particular, the use of 3D blocky particles represented as super-quadrics results in excellent agreement between the DEM predictions and the experiments at the fixed wall and good agreement elsewhere. The particle shape plays a critical role in determining the shear strength of the material and therefore the failure of the particle bed, the formation of shear bands and therefore its flow characteristics.
ABSTRACT The performance of screw feeders is affected by the design of their three major componen... more ABSTRACT The performance of screw feeders is affected by the design of their three major components (hopper, screw casing and screw), the rotational speed of the screw, the inclination of the screw, and the properties and size distribution of the bulk material. In this paper we focus on the application of the Discrete Element Method (DEM) to simulate the transport of granular material by screw feeders. Examples of 3D models of enclosed screw feeders are presented along with detailed predictions of their performance, namely: (1) the effect on the mass flow rate of a screw feeder as its angle of inclination was increased; (2) the effect on the mass flow rate of a screw feeder having a shaft-less screw as its inclination increased; (3) the degree to which particles of different sizes segregate as they are pushed along the screw feeder; and (4) the nature of the draw down of the bulk material from a hopper into the screw casing by the rotating screw.
Granular flows in shear cells have been extensively studied using the Discrete Element Method (DE... more Granular flows in shear cells have been extensively studied using the Discrete Element Method (DEM) over the last two decades. These studies have typically been performed using the soft-sphere approach where deformation is assumed elastic and small relative to the characteristic grain scale. Consequently internal stresses and strains are not able to be modelled. As a first step towards addressing these limitations, we introduce a variant of DEM, the Distributed Contact DEM (DCDEM). This method models distributed normal and frictional contacts. In this initial implementation plastic deformation is not simulated and elastic deformation is simulated by permitting overlap as in traditional DEM. The method is compared against standard DEM for an oblique and normal impact and a granular shear cell in the small deformation limit. NOMENCLATURE C damping coefficient (Ns/m) ds segment length (m) dx overlap (m) F force (N) J moment of inertia (kg m 2 ) k spring stiffness (N/m) m mass (kg) Mo moment (N m) N g number of grains N p number of points per grain R grain radius (m) t time (s) µ dynamic friction coefficient ν Poisson's ratio w z spin (rad/s)
ABSTRACT We investigate the fall of planar granular columns in a quasi-static regime using a comb... more ABSTRACT We investigate the fall of planar granular columns in a quasi-static regime using a combination of laboratory experiments and DEM modelling. Columns made of alternatively coloured sand layers are initially laid out in a box and then released when a retaining wall is set in slow motion with constant speed. The two-dimensional flow involves failure of the granular material along multiple slip planes at different stages of the deformation leading to complex folding patterns. 2D DEM simulation is able to qualitatively reproduce a range of essential elements of this flow with particle shape being an important contributor to the mobilisation of specific slip planes.
Minerals Engineering, Dec 1, 2006
Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is... more Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot ...
Astrophys J, 1989
Several new families of low-resonance periodic orbits have been found for the slowly rotating tri... more Several new families of low-resonance periodic orbits have been found for the slowly rotating triaxial Schwarzschild potential. Their bifurcation structure is complicated and involves a number of equatorial plane instability strips and three-dimensional cascade structures. Their orbital behavior and stability are also examined.
Page 1. Progress in Computational Fluid Dynamics, Vol. 10, Nos. 5/6, 2010 327 Copyright © 2010 In... more Page 1. Progress in Computational Fluid Dynamics, Vol. 10, Nos. 5/6, 2010 327 Copyright © 2010 Inderscience Enterprises Ltd. Screw conveyor performance: comparison of discrete element modelling with laboratory experiments Philip J. Owen* and Paul W. Cleary ...
The flow of granular media is both intriguing and up to now barely understood. A recently initiat... more The flow of granular media is both intriguing and up to now barely understood. A recently initiated series of experiments systematically studies granular flow in a simple setting, namely the collapse of a granular column onto a horizontal plane. In this paper, we present computational studies of the axi-symmetric collapse of granular columns using the three-dimensional Discrete Element Method. We consider a single experiment and explore the sensitivity of the result when varying key unknown model and physical parameters for spherical particles. The observations allow us to give an upper bound on the dynamic friction coefficient.
Progress in Computational Fluid Dynamics an International Journal, 2012
ABSTRACT Understanding how the permeability of a porous medium changes as function of solid fract... more ABSTRACT Understanding how the permeability of a porous medium changes as function of solid fraction and pore geometry is vital in many significant areas. Here, we construct a number of different porous media via computer methods. We then simulate the flow of a viscous liquid through the solid packing using the Smoothed Particle Hydrodynamics (SPH) and Lattice Boltzmann (LB) methods. Qualitative comparisons of flow between the two methods are generally good as are the quantitative permeability comparisons. The relative computational efficiency of both methods is examined with the LB method being superior to SPH for this application.
Xxv International Mineral Processing Congress 2010 Impc 2010, 2010
ABSTRACT Most DEM analyses of ball and stirred mills reported to date have considered only media ... more ABSTRACT Most DEM analyses of ball and stirred mills reported to date have considered only media motion and its interaction with the mill lifter configuration. For SAG mills, a large fraction of the feed material can already be well represented in DEM models. But for other mill types with much finer feed, the number of feed particles has been prohibitive to include them directly in the calculations. The C-MIS code is now sufficiently powerful to allow inclusion of ore particles within a short periodic section of a small pilot (or large lab) scale mill. This provides the opportunity to better understand the effect of media on the interstitial bed of powder and of the powder on the media. In this paper, the complete pilot mill was first simulated with media only included. A truncated size distribution was then used to represent ore particles in a periodic simulation of about one tenth of the mill length. The results allowed for analysis of the effect of rock on the overall flow, and the influence of the fl ow and collisional environment on the fine ore particles. The normal, shear and total energy consumptions were also analysed for different powder fi ll levels.
... simulations. Delaney, Gary W., Cleary, Paul W., Sinnott, Matt D. and Morrison, Rob D. (2010).... more ... simulations. Delaney, Gary W., Cleary, Paul W., Sinnott, Matt D. and Morrison, Rob D. (2010). ... Statistics. Created: Thu, 09 Dec 2010, 13:39:12 EST by Karen Holtham on behalf of Julius Kruttschnitt Mineral Research Centre - Detailed History. ...
Progress in Computational Fluid Dynamics an International Journal, Mar 20, 2015
... This ensures that the density variation is less than 1% and the flow can be regarded asincomp... more ... This ensures that the density variation is less than 1% and the flow can be regarded asincompressible. ... Improvements to both product quality and process productivity can be brought about through improved die design. ... (1999) compared isothermal SPH simulations with water ...
Minerals Engineering, Nov 1, 2009
Banana screens are often used for high capacity separation of iron ore, coal and aggregates into ... more Banana screens are often used for high capacity separation of iron ore, coal and aggregates into different size fractions. They consist of one or more curved decks that are fitted with screen panels with arrays of square or rectangular holes. The screen structure is vibrated while a dense stream of particles flows over it and is separated according to size. The material discharging from the top of the deck is the oversize and may become a coarse product or be crushed and recycled to the screen feed. The material falling through the deck can be further separated by additional decks below. Each lower deck returns a product stream and the material passing out through the bottom deck is the undersize. In this paper, Discrete Element Method (DEM) is used to explore the separation performance of a full industrial scale double deck banana screen for a peak acceleration of 5g. The separation efficiency of each deck is analysed and the individual contributions of each screen panel are assessed using outputs from the model. Residence time distributions for particles on each deck provide insight into both the transport characteristics along the deck and the separation performance through each deck. The top and bottom decks have very different flow behaviour with very different bed structure and motion. The stresses applied by the flowing particles to the screen cloths and the impact and abrasive wear on the screen surfaces are evaluated. Finally, the energy absorbed by particles provides insight into the extent of particle degradation produced by transiting the screen.
The aim of this work was to perform a quantitative experimental investigation of two-dimensional ... more The aim of this work was to perform a quantitative experimental investigation of two-dimensional buoyancyinduced flows using a Schlieren method. As known, the Schlieren technique utilizes the refraction of light rays to display a pattern related to the temperature field. The employed Schlieren system makes use of an opaque filament to identify regions of fluid deflecting light rays by the same amount. An iterative inverse technique was developed to reconstruct the temperature field from optical data. After a description of the experimental technique and of the data processing features, results concerning the temperature profile reconstruction for natural convective flows are presented. Attention is devoted to air-bouyancy flows induced by a single heated vertical plate and by an array of four heated vertical plates. Reconstructed temperature data are compared with theoretical predictions and with direct temperature measurements performed by thermocouples.
CFD modelling is a powerful, but largely under-utilised tool for biomedical applications. In part... more CFD modelling is a powerful, but largely under-utilised tool for biomedical applications. In particular, it has great potential for helping us better understand the mechanisms responsible for cardiovascular disease such as artherosclerosis and thrombi formation. Flow behaviour in blood vessels has been shown to depend strongly on features of the local geometry such as branching, bending, and regions of flow constriction. The simplest blood flow models only consider steady flow. However within the circulatory system, the periodic nature of the cardiac cycle induces a pulsatile, unsteady flow. This periodic pressure perturbation is expected to have significant implications for localised flow velocities and stress distributions.
Minerals Engineering, Dec 1, 2006
Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is... more Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot ...
Minerals Engineering, Aug 1, 2009
Grinding of clinker for cement production is often performed in a two chamber ball mill. In the f... more Grinding of clinker for cement production is often performed in a two chamber ball mill. In the first shorter chamber, raw feed is ground using media consisting of large balls. The ground product of the first chamber exits through a discharge grate and enters the second longer chamber. Here smaller balls are used to grind the product material even finer. In this paper we analyse the charge motion, short term ball segregation processes and energy utilisation in a 4 m diameter cement ball mill using DEM. The power draw predicted is consistent with the rated power of the mill. The energy dissipation in the mill is dominated by shear interaction. The gentle liner profiles ensure that few balls move on cataracting trajectories. The distribution of energy utilisation between the different size media fractions is explored as are differences in the collisional environment between the two mill chambers.
Surface and Coatings Technology, 2014
ABSTRACT Cold spray is a manufacturing process that has proved to be a valuable technique for pro... more ABSTRACT Cold spray is a manufacturing process that has proved to be a valuable technique for producing high strength metallic coatings. It has been extensively studied in recent years, both experimentally and computationally. Among the various modelling investigations in the literature, a large number have considered the problem of a single particle impacting a substrate by means of a continuum technique, most commonly the finite element method. These models that have been used previously are generally based on two inadequate assumptions, namely 1) both particle and substrate are assumed to initially be at room temperature, and 2) the experimentally observed increase in strain rate sensitivity of the flow stress at high strain rates is ignored. To investigate the combined effect of temperature and strain rates, a three-dimensional model of a single particle impact with a metallic substrate has been developed using Smoothed Particle Hydrodynamics. This meshless method is ideally suited to the simulation of Cold Spray as very large material deformations can be readily accommodated, whereas this is often a significant difficulty in mesh based techniques. A Cu-on-Cu impact was considered and quantitative comparisons with experimental cross sections were conducted. It was found that predictions within 5% of the experimental data could be achieved only when both the softening effect due to the initial thermal field and the hardening effect due to the very high strain rates were included in the model. In contrast ignoring these effects led to results that had as much as 50% variation compared to experiments. The model described in this paper is a robust tool that will enable quantitative predictions of cold spray impacts and help further optimize the process.
Publication details, including instructions for authors and subscription information: To cite thi... more Publication details, including instructions for authors and subscription information: To cite this Article Owen, P. J., Cleary, P. W. and Mériaux, C.'Quasi-static fall of planar granular columns: comparison of 2D and 3D discrete element modelling with laboratory experiments', Geomechanics and Geoengineering, 4: 1, 55 — 77 We investigate the fall of planar granular columns in a quasi-static regime using a combination of laboratory experiments and simulations using the discrete element method (DEM). Columns made of alternately coloured sand layers are initially laid out in a box and then released when a retaining wall is set in slow motion with constant speed. The flow of the sand involves failure of the granular material along multiple slip planes at different stages of the deformation, leading to complex flow patterns. DEM simulations, in 2D and 3D, are able to qualitatively and quantitatively reproduce a range of essential elements of this flow, with particle shape being an important contributor to the mobilisation of specific slip planes. We also examine the sensitivity of the DEM predictions to changes in the operating, material and simulation parameters. We find that DEM predictions are invariant to changes of moving wall speed, spring stiffness, particle-particle friction and particle-wall friction. Conversely, they are quite sensitive to the shape of the particles. In particular, the use of 3D blocky particles represented as super-quadrics results in excellent agreement between the DEM predictions and the experiments at the fixed wall and good agreement elsewhere. The particle shape plays a critical role in determining the shear strength of the material and therefore the failure of the particle bed, the formation of shear bands and therefore its flow characteristics.
ABSTRACT The performance of screw feeders is affected by the design of their three major componen... more ABSTRACT The performance of screw feeders is affected by the design of their three major components (hopper, screw casing and screw), the rotational speed of the screw, the inclination of the screw, and the properties and size distribution of the bulk material. In this paper we focus on the application of the Discrete Element Method (DEM) to simulate the transport of granular material by screw feeders. Examples of 3D models of enclosed screw feeders are presented along with detailed predictions of their performance, namely: (1) the effect on the mass flow rate of a screw feeder as its angle of inclination was increased; (2) the effect on the mass flow rate of a screw feeder having a shaft-less screw as its inclination increased; (3) the degree to which particles of different sizes segregate as they are pushed along the screw feeder; and (4) the nature of the draw down of the bulk material from a hopper into the screw casing by the rotating screw.
Granular flows in shear cells have been extensively studied using the Discrete Element Method (DE... more Granular flows in shear cells have been extensively studied using the Discrete Element Method (DEM) over the last two decades. These studies have typically been performed using the soft-sphere approach where deformation is assumed elastic and small relative to the characteristic grain scale. Consequently internal stresses and strains are not able to be modelled. As a first step towards addressing these limitations, we introduce a variant of DEM, the Distributed Contact DEM (DCDEM). This method models distributed normal and frictional contacts. In this initial implementation plastic deformation is not simulated and elastic deformation is simulated by permitting overlap as in traditional DEM. The method is compared against standard DEM for an oblique and normal impact and a granular shear cell in the small deformation limit. NOMENCLATURE C damping coefficient (Ns/m) ds segment length (m) dx overlap (m) F force (N) J moment of inertia (kg m 2 ) k spring stiffness (N/m) m mass (kg) Mo moment (N m) N g number of grains N p number of points per grain R grain radius (m) t time (s) µ dynamic friction coefficient ν Poisson's ratio w z spin (rad/s)
ABSTRACT We investigate the fall of planar granular columns in a quasi-static regime using a comb... more ABSTRACT We investigate the fall of planar granular columns in a quasi-static regime using a combination of laboratory experiments and DEM modelling. Columns made of alternatively coloured sand layers are initially laid out in a box and then released when a retaining wall is set in slow motion with constant speed. The two-dimensional flow involves failure of the granular material along multiple slip planes at different stages of the deformation leading to complex folding patterns. 2D DEM simulation is able to qualitatively reproduce a range of essential elements of this flow with particle shape being an important contributor to the mobilisation of specific slip planes.
Minerals Engineering, Dec 1, 2006
Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is... more Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot ...
Astrophys J, 1989
Several new families of low-resonance periodic orbits have been found for the slowly rotating tri... more Several new families of low-resonance periodic orbits have been found for the slowly rotating triaxial Schwarzschild potential. Their bifurcation structure is complicated and involves a number of equatorial plane instability strips and three-dimensional cascade structures. Their orbital behavior and stability are also examined.
Page 1. Progress in Computational Fluid Dynamics, Vol. 10, Nos. 5/6, 2010 327 Copyright © 2010 In... more Page 1. Progress in Computational Fluid Dynamics, Vol. 10, Nos. 5/6, 2010 327 Copyright © 2010 Inderscience Enterprises Ltd. Screw conveyor performance: comparison of discrete element modelling with laboratory experiments Philip J. Owen* and Paul W. Cleary ...
The flow of granular media is both intriguing and up to now barely understood. A recently initiat... more The flow of granular media is both intriguing and up to now barely understood. A recently initiated series of experiments systematically studies granular flow in a simple setting, namely the collapse of a granular column onto a horizontal plane. In this paper, we present computational studies of the axi-symmetric collapse of granular columns using the three-dimensional Discrete Element Method. We consider a single experiment and explore the sensitivity of the result when varying key unknown model and physical parameters for spherical particles. The observations allow us to give an upper bound on the dynamic friction coefficient.
Progress in Computational Fluid Dynamics an International Journal, 2012
ABSTRACT Understanding how the permeability of a porous medium changes as function of solid fract... more ABSTRACT Understanding how the permeability of a porous medium changes as function of solid fraction and pore geometry is vital in many significant areas. Here, we construct a number of different porous media via computer methods. We then simulate the flow of a viscous liquid through the solid packing using the Smoothed Particle Hydrodynamics (SPH) and Lattice Boltzmann (LB) methods. Qualitative comparisons of flow between the two methods are generally good as are the quantitative permeability comparisons. The relative computational efficiency of both methods is examined with the LB method being superior to SPH for this application.
Xxv International Mineral Processing Congress 2010 Impc 2010, 2010
ABSTRACT Most DEM analyses of ball and stirred mills reported to date have considered only media ... more ABSTRACT Most DEM analyses of ball and stirred mills reported to date have considered only media motion and its interaction with the mill lifter configuration. For SAG mills, a large fraction of the feed material can already be well represented in DEM models. But for other mill types with much finer feed, the number of feed particles has been prohibitive to include them directly in the calculations. The C-MIS code is now sufficiently powerful to allow inclusion of ore particles within a short periodic section of a small pilot (or large lab) scale mill. This provides the opportunity to better understand the effect of media on the interstitial bed of powder and of the powder on the media. In this paper, the complete pilot mill was first simulated with media only included. A truncated size distribution was then used to represent ore particles in a periodic simulation of about one tenth of the mill length. The results allowed for analysis of the effect of rock on the overall flow, and the influence of the fl ow and collisional environment on the fine ore particles. The normal, shear and total energy consumptions were also analysed for different powder fi ll levels.
... simulations. Delaney, Gary W., Cleary, Paul W., Sinnott, Matt D. and Morrison, Rob D. (2010).... more ... simulations. Delaney, Gary W., Cleary, Paul W., Sinnott, Matt D. and Morrison, Rob D. (2010). ... Statistics. Created: Thu, 09 Dec 2010, 13:39:12 EST by Karen Holtham on behalf of Julius Kruttschnitt Mineral Research Centre - Detailed History. ...
Progress in Computational Fluid Dynamics an International Journal, Mar 20, 2015
... This ensures that the density variation is less than 1% and the flow can be regarded asincomp... more ... This ensures that the density variation is less than 1% and the flow can be regarded asincompressible. ... Improvements to both product quality and process productivity can be brought about through improved die design. ... (1999) compared isothermal SPH simulations with water ...
Minerals Engineering, Nov 1, 2009
Banana screens are often used for high capacity separation of iron ore, coal and aggregates into ... more Banana screens are often used for high capacity separation of iron ore, coal and aggregates into different size fractions. They consist of one or more curved decks that are fitted with screen panels with arrays of square or rectangular holes. The screen structure is vibrated while a dense stream of particles flows over it and is separated according to size. The material discharging from the top of the deck is the oversize and may become a coarse product or be crushed and recycled to the screen feed. The material falling through the deck can be further separated by additional decks below. Each lower deck returns a product stream and the material passing out through the bottom deck is the undersize. In this paper, Discrete Element Method (DEM) is used to explore the separation performance of a full industrial scale double deck banana screen for a peak acceleration of 5g. The separation efficiency of each deck is analysed and the individual contributions of each screen panel are assessed using outputs from the model. Residence time distributions for particles on each deck provide insight into both the transport characteristics along the deck and the separation performance through each deck. The top and bottom decks have very different flow behaviour with very different bed structure and motion. The stresses applied by the flowing particles to the screen cloths and the impact and abrasive wear on the screen surfaces are evaluated. Finally, the energy absorbed by particles provides insight into the extent of particle degradation produced by transiting the screen.
The aim of this work was to perform a quantitative experimental investigation of two-dimensional ... more The aim of this work was to perform a quantitative experimental investigation of two-dimensional buoyancyinduced flows using a Schlieren method. As known, the Schlieren technique utilizes the refraction of light rays to display a pattern related to the temperature field. The employed Schlieren system makes use of an opaque filament to identify regions of fluid deflecting light rays by the same amount. An iterative inverse technique was developed to reconstruct the temperature field from optical data. After a description of the experimental technique and of the data processing features, results concerning the temperature profile reconstruction for natural convective flows are presented. Attention is devoted to air-bouyancy flows induced by a single heated vertical plate and by an array of four heated vertical plates. Reconstructed temperature data are compared with theoretical predictions and with direct temperature measurements performed by thermocouples.
CFD modelling is a powerful, but largely under-utilised tool for biomedical applications. In part... more CFD modelling is a powerful, but largely under-utilised tool for biomedical applications. In particular, it has great potential for helping us better understand the mechanisms responsible for cardiovascular disease such as artherosclerosis and thrombi formation. Flow behaviour in blood vessels has been shown to depend strongly on features of the local geometry such as branching, bending, and regions of flow constriction. The simplest blood flow models only consider steady flow. However within the circulatory system, the periodic nature of the cardiac cycle induces a pulsatile, unsteady flow. This periodic pressure perturbation is expected to have significant implications for localised flow velocities and stress distributions.
Minerals Engineering, Dec 1, 2006
Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is... more Stirred mills are becoming increasingly used for fine and ultra-fine grinding. This technology is still poorly understood when used in the mineral processing context. This makes process optimisation of such devices problematic. 3D DEM simulations of the flow of grinding media in pilot ...
Minerals Engineering, Aug 1, 2009
Grinding of clinker for cement production is often performed in a two chamber ball mill. In the f... more Grinding of clinker for cement production is often performed in a two chamber ball mill. In the first shorter chamber, raw feed is ground using media consisting of large balls. The ground product of the first chamber exits through a discharge grate and enters the second longer chamber. Here smaller balls are used to grind the product material even finer. In this paper we analyse the charge motion, short term ball segregation processes and energy utilisation in a 4 m diameter cement ball mill using DEM. The power draw predicted is consistent with the rated power of the mill. The energy dissipation in the mill is dominated by shear interaction. The gentle liner profiles ensure that few balls move on cataracting trajectories. The distribution of energy utilisation between the different size media fractions is explored as are differences in the collisional environment between the two mill chambers.